1. Field of the Invention
The present invention relates to an imaging optical system, and more particularly, to a subminiature image optical system mounted on a portable device such as a mobile communication terminal and a personal digital assistant or used for a monitoring camera and a digital camera.
2. Description of the Related Art
In general, mobile communication terminals had only functions of basic communication at their incipient stage. However, with increased use, the mobile communication terminals are required to have diversified functions ranging from photographing to image transmission and video communication, continuously evolving in their functions and services. Recently, a new expanded concept of mobile communication terminal by integrating digital camera technology with mobile phone technology, i.e., so called camera phones or camera mobile phones are significantly attracting attention.
In particular, the imaging optical system mounted on the camera phone is not only required to be miniaturized, lightweight and low cost, but also have high resolution since the pixel size of an image sensor formed of a charge-coupled device (CCD) or a complementary metal oxide semiconductor (CMOS) used in the imaging optical system is decreasing.
Also, a wide viewing angle is required with respect to the imaging optical system using the image sensor
In order to satisfy miniaturization and low cost, the imaging optical system mounted on a small device such as a mobile phone needs to have a small number of lenses as possible, but this restricts a degree of freedom in designing and undermines the optical capabilities.
Therefore, there is required a subminiature imaging optical system capable of being easily miniaturized while having high resolution and a wide viewing angle.